In certain types of medical emergencies, Cardiopulmonary Resuscitation (CPR) needs to be delivered to a patient. CPR includes repeatedly compressing the chest of the patient, to cause their blood to circulate some. CPR also includes delivering rescue breaths to the patient. A number of people are trained in CPR, just in case, even though they are not trained in the medical professions.
The chest compressions are intended to prevent damage to organs like the brain. In some instances, the chest compressions merely maintain the patient, until a more definite therapy is made available, such as defibrillation. Defibrillation is an electrical shock deliberately delivered to a person, in the hope of correcting their heart rhythm.
A problem is that CPR is sometimes ineffective for preventing damage to the patient. That can happen whether or not the rescuer who performs the CPR is part of the medical profession. The most frequent example of such ineffectiveness is compressions that are not deep enough, or not frequent enough. Even the best trained rescuers can become fatigued after delivering CPR, with the compressions deteriorating in quality. And that is without even accounting for the emotions of the moment, which might impact a lay rescuer.
The risk of ineffective chest compressions has been addressed in part by defibrillator manufacturers. Some defibrillators nowadays issue verbal and visual prompts and other instructions as to how CPR is to be performed. These are often according to the guidelines of medical experts, such as the American Heart Association. These prompts and other instructions and can help the rescuer focus better, even if the latter cannot remember their training.
The risk of ineffective chest compressions has been additionally addressed with CPR feedback devices. These devices actually detect the depth and frequency of compressions that the rescuer is performing, and give feedback to the rescuer that specifically attuned to what the rescuer is doing. This feedback can be in accordance with how well the rescuer is meeting the above mentioned guidelines, especially in achieving the indicated depth of compressions.
Reaching the appropriate depth is difficult. The recommended depth is a range. If the actual depth is less than the range, not enough blood is moved within the patient. If the depth exceeds the range, the patient's ribs may break. And, even for experienced rescuers, it is sometimes hard to discern the appropriate depth. Reaching the appropriate depth is even more difficult if the patient is on a flexible mattress that partly recedes, as the rescuer is pushing from the top. And CPR compressions are even harder in the first place, if the rescuer has to deliver them in a moving ambulance.
The risk of ineffective chest compressions has been moreover addressed with CPR chest compression machines. Such machines have been known by a number of names, such as mechanical CPR devices, cardiac compressors, external chest compression machines, and so on.
CPR chest compression machines repeatedly compress and release the chest of the patient. Such machines can be programmed so that they will compress and release at the recommended rate, and always reach a specific depth within the recommended range.
A problem with CPR chest compression machines is that the person may shift and/or slide within the CPR chest compression structure if the CPR chest compression structure is tilted from the horizontal. This may happen even if the person is harnessed in the CPR chest compression machine.
Shifting and sliding can be caused by the patient and/or compression structure being moved up or down stairs, for example. If the person slides in the CPR chest compression machine, then the piston, or equivalent chest compressing component, of the CPR chest compression structure will not make contact with the person at the proper location on the person's chest. It is sometimes advised to not operate, or operate with caution, the CPR chest compression machine, during periods of time when the person and/or CPR chest compression structure are tilted more than a critical value. Such limitations may be difficult to remember, or may be disregarded, during actual resuscitation use of the CPR chest compression machine, to the possible detriment of the effectiveness of the chest compressions being provided.